Novel and efficient synthetic path to proaporphine alkaloids:: Total synthesis of (±)-stepharine and (±)-pronuciferine

A novel synthetic path to proaporphine alkaloids was established by employing aromatic oxidation with a hypervalent iodine reagent, where an unprecedented carbon-carbon bond forming reaction between the para-position of a phenol group and an enamide-carbon took place smoothly to give the desired spiro-cyclohexadienone.